1. Field of the Invention
The present invention relates to a method for forming a pattern capable of forming a film as selected by controlling wettability of a surface where the film is to be formed, a method for manufacturing a light emitting device having a light emitting element using the method for forming a pattern, and a light emitting device.
A light emitting element is an element having a structure in which a film containing an organic compound (hereinafter referred to as a layer containing an organic compound) is provided between a pair of electrodes, and fluorescence or phosphorescence can be obtained by application of an electric field.
The light emitting device refers to an image display device, a light emitting device, or a light source (including a lighting device). Further, the light emitting device includes any of the following modules in its category: a module in which a connector such as a flexible printed circuit (FPC), tape automated bonding (TAB) tape, or a tape carrier package (TCP) is attached to a light emitting device; a module having TAB tape or a TCP provided with a printed wiring board at the end thereof; and a module having an integrated circuit (IC) directly mounted on a light emitting device by a chip on glass (COG) method.
2. Description of the Related Art
A droplet-discharging method such as an ink-jet method has been used as a method for forming a pattern. In this method, specifically, droplets of a liquid material containing a material for forming a pattern are discharged to a desired position to form a pattern, and various patterns can be formed without using a photolithography process or the like. Thus, a droplet-discharging method has an advantage that consumption of the material can be suppressed to the minimum.
When a pattern is formed by a droplet-discharging method, in order to improve accuracy in applying a liquid material to a part where a film is to be formed, a method in which only the part where a film is to be formed over the substrate is modified to be lyophilic and other parts are modified to be liquid-repellent is used.
As one example of the above method, a method for forming a pattern is known, in which, after fluoroalkylsilane (FAS) or the like is applied to the entire surface of a substrate so that the entire surface is modified to be liquid-repellent, only a part where a film is to be formed is irradiated with ultraviolet rays using a metal mask, and the part where a film is to be formed is modified to be lyophilic (for example, refer to Reference 1: Japanese Published Patent Application No. 2005-93691).
In addition, as another example, a method for forming a pattern is known, in which, when a layer containing an organic compound of a light emitting element is formed as a pattern, a layer containing a photocatalyst which includes photocatalytic particles and a binder is formed over one electrode, only the electrode is irradiated with light in pattern to decompose active constituents of the binder, and only the surface of the electrode is modified to be lyophilic, so that the layer containing an organic compound is formed over the electrode (for example, refer to Reference 2: Japanese Published Patent Application No. 2003-332080).
However, these methods have problems in that a specific metal mask is necessary so that light irradiation is partially performed, and the number of manufacturing steps is increased since a photolithography technique is used for irradiation in pattern. Further, in the latter example, there are also problems in that when the amount of the binder is increased to smooth the layer containing a photocatalyst, constituents of the binder with an insulating property remain on the electrode which is modified to be lyophilic, and electric characteristics of the light emitting element are degraded.